Alternating current light-emitting diode lamp adaptive to ambient luminance

Abstract

An AC LED lamp adaptive to ambient luminance has a lamp shell, an LED lamp board, an LED driving circuit and a luminance sensor. The LED lamp board, the LED driving circuit and the luminance sensor are mounted inside the lamp shell and are electrically connected to each other. The luminance sensor is mounted on the LED lamp board, is capable of sensing light emitted from the LED lamp board. Multiple LED elements on the LED lamp board are alternately driven to turn on and turn off and a luminance signal is sensed by the luminance sensor while the LED elements are driven to turn off. As the luminance signal contains an ambient luminance only, accurate ambient luminance for the lamp can be therefore acquired.

What is claimed is: 
     
       1. An alternating current (AC) light-emitting diode (LED) lamp adaptive to ambient luminance comprising:
 a lamp shell having a light exit surface; 
 an LED lamp board mounted inside the lamp shell and having multiple LED elements mounted thereon, and facing the light exit surface; 
 a luminance sensor mounted inside the lamp shell and facing the light exit surface; and 
 an LED driving circuit mounted inside the lamp shell and electrically connected to the LED lamp board and the luminance sensor so that the LED elements on the LED lamp board are alternately driven to turn on or turn off and the LED driving circuit driving circuit receives a luminance signal is sensed by the luminance sensor while the LED elements are driven to turn off. 
 
     
     
       2. The AC LED lamp as claimed in  claim 1 , wherein the LED driving circuit has:
 a full-bridge rectifier connected to an AC power source and the LED lamp board and converting the AC power into a half-wave DC power, wherein a positive output terminal of the full-bridge rectifier is connected to an anode of the LED lamp board; 
 a voltage-controlled transistor, wherein one terminal of the voltage-controlled transistor is connected to the cathode of the LED lamp board; 
 a current detection unit connected between another terminal of the voltage-controlled transistor and a negative output terminal of the full-bridge rectifier to constitute a power loop through the voltage-controlled transistor; and 
 a control unit connected to a control terminal of the voltage-controlled transistor and connected to the current detection unit through a low-pass filter to detect a turn-on current of the LED lamp board and control a voltage of the voltage-controlled transistor, so as to adjust an average current of the LED lamp board. 
 
     
     
       3. The AC LED lamp as claimed in  claim 2 , wherein
 the control unit has a preset fixed luminance range delimited by a lower bound and an upper bound and is built in with an automatic luminance control procedure to control a luminance of light emitted by the LED lamp board according to an ambient luminance; 
 the automatic luminance control procedure has steps of:
 calculating a current luminance value of light emitted by the LED lamp board; 
 calculating a current ambient luminance value; 
 summing up the current luminance value and the current ambient luminance value to obtain a total luminance value; and 
 determining if the total luminance value exceeds a range of the fixed luminance range, if the total luminance value is greater than the lower bound and less than the upper bound of the fixed luminance range, maintaining the current average current of the LED lamp board, if the total luminance value is less than the lower bound of the fixed luminance range, increasing the average current, and if the total luminance value is greater than the lower bound of the fixed luminance range, decreasing the average current. 
 
 
     
     
       4. The AC LED lamp as claimed in  claim 3 , wherein the step of calculating a current luminance value further has steps of:
 comparing a driving voltage of the LED lamp board with a peak voltage value of the half-wave DC power to calculate a turn-on cycle of the LED lamp board; 
 detecting the turn-on current while the LED lamp board is lit through the current detection unit; 
 calculating the average current of the LED lamp board; and 
 obtaining the luminance value of light emitted by the LED lamp board according to the average current. 
 
     
     
       5. The AC LED lamp as claimed in  claim 4 , wherein the LED elements of the LED lamp board are connected to each other by one of series connection, parallel connection and series-parallel connection. 
     
     
       6. The AC LED lamp as claimed in  claim 4 , wherein the voltage-controlled transistor is an MOSFET or an IGBT. 
     
     
       7. The AC LED lamp as claimed in  claim 4 , wherein the current detection unit is a resistor. 
     
     
       8. The AC LED lamp as claimed in  claim 3 , wherein the LED elements of the LED lamp board are connected to each other by one of series connection, parallel connection and series-parallel connection. 
     
     
       9. The AC LED lamp as claimed in  claim 3 , wherein the voltage-controlled transistor is an MOSFET or an IGBT. 
     
     
       10. The AC LED lamp as claimed in  claim 3 , wherein the current detection unit is a resistor. 
     
     
       11. The AC LED lamp as claimed in  claim 2 , wherein the LED elements of the LED lamp board are connected to each other by one of series connection, parallel connection and series-parallel connection. 
     
     
       12. The AC LED lamp as claimed in  claim 2 , wherein the voltage-controlled transistor is an MOSFET or an IGBT. 
     
     
       13. The AC LED lamp as claimed in  claim 2 , wherein the current detection unit is a resistor. 
     
     
       14. The AC LED lamp as claimed in  claim 1 , wherein the LED elements of the LED lamp board are connected to each other by one of series connection, parallel connection and series-parallel connection. 
     
     
       15. The AC LED lamp as claimed in  claim 1 , wherein the voltage-controlled transistor is an MOSFET or an IGBT. 
     
     
       16. The AC LED lamp as claimed in  claim 1 , wherein the current detection unit is a resistor.